The present invention relates to optical instruments for binocular visioned people which is useful for various applications such as surveying, sighting and orienting.
Laser light sources have been increasingly used in surveying and various optical sighting and orienting systems. These typically involve a high power laser projecting light upon a distant target and require certain protective measures to avoid damage to the human eye. Moreover, the laser beam expands in diameter with distance. When used for gun sighting, the laser beam provides a path to the sighting device. In other sighting applications various forms of lighted reticles are used such as in optical instruments where the illuminated reticle is superposed on the image of a scene, such as a target in which the illuminated reticle is viewed. In such systems, one eye is closed and the scene with the superposed reticle superposed thereon is viewed through the one open eye. In other systems such as in photogrammatic stereoplotters, periscopes, etc., a light spot reticle is optically added to a stereo scene, either directly or indirectly through half-silvered mrrors, prisms, etc.
The present invention depends on the phenomena of the human brain which fuses images viewed by one eye with images viewed by the other eye to superpose a collimated light spot reticle upon the image of a scene viewed through the other eye. In a preferred embodiment, a low powered light point source of visible radiation having a wavelength in the range of 200-900 NM (nanometer) and 660NM has been found to be very useful, collimated and surrounded by an optical void (as defined herein, an optical void is a black or non-visible background immediately surrounding the point light source) which substantially excludes from vision in one eye all objects except the collimated light point source of visible monochromatic radiation. In this context, it is not required that the observer's eye be positioned directly on the instrument to exclude the remainder of the scene from the normal field of vision of the eye that is viewing the point light source. The optical void can be created by locating the collimated light point source of visible monochromatic radiation of wavelength in a tubular body member which is internally coated with radiation absorbent material such as a black paint or an otherwise non-reflective coating. In some cases, there can be a halo effect created by an incomplete optical void which can help to locate the point light source for the observer. In a preferred embodiment, the point light source is circular and about 1 mm in diameter.
When a scene is observed using the one eye (with or without magnification) and the other eye of an individual is viewing the collimated light point source of visible monochromatic radiation, due to the optical fusion property of the human brain, the point light source appears centrally in the fused scene.
The term "low power" is meant a light source which does not require protective measures for the eye. The combination of high power sources with some form of energy attenuation effected prior to forming the point light source is also encompassed by this term. Typical PN junction diodes or optoelectronic light source useful in the practice of this invention operate in the under 100 milliwatt range.
When the collimated light point source is mounted on an orientable support structure, such as surveyor's transit tripod and leveling structure, and plumbed and leveled in the same fashion as plumbing and leveling a surveyor's transit, and the collimated light point source is viewed through one eye and the other eye views the scene, the collimated light point source which has been leveled is fused into the scene viewed, by the other eye. A stadia rod, for example, will have the light spot positioned at a precise target point and the normal measurements are made. This results in a higher degree of measurement accuracy than the best available optical level, and at longer ranges. When mounted on a rifle, for example, and the collimated light source has its axis oriented with the axis of the rifle barrel, and the target viewed with one eye, wherever the light spot appears in the fused scene, the axis of the rifle barrel is oriented precisely with the position of the light spot at the target. The system of this invention is impervious to working conditions (condensation, rising thermal waves) and variable light conditions. It has lower instrument costs, minimal power and weight requirements, and is simpler to use and has a range limited only by line of vision. There is no difference in whether the observer has corrective lenses (glasses, contact lenses, tinted, etc.) or not.
In the preferred embodiment, a 660NM wavelength produces optimal visual fusion of the two images. The optical void or black surround enhances the visual fusion of the two images. In addition, the red band has less permanency on the human retina. Moreover, in many surveying, aircraft landing systems, etc., the background is predominantly green or another background color on which the "red bond" light stands out more prominently. While the 660NM wavelength point light source has been found to be most preferable, it is to be understood the broader aspects of the invention encompass other wavelengths.
In other sighting situations, when the device is mounted on an orientable support surface, such as a light on a particular landing spot (in the scene viewed by the other eye) and by maintaining the spot of light on that point through maneuvering of the helicopter aircraft, effect a proper and safe landing.
Thus, the present invention provides an improved optical sighting instrument which requires the use of two eyes and the optical fusion property of the human brain but, in comparison with the best optical level, for example, results in:
(1) greater accuracy, PA1 (2) impervious to: PA1 (3) minimal power requirements, PA1 (4) range limited only by line of sight, PA1 (5) simpler to use, PA1 (6) minimal adjustments previous to use.
(a) condensation, PA2 (b) rising thermal waves, PA2 (c) full functions under various light conditions,
The orientable support referred to above can be a surveyor's instrument base, such as a transit, level, etc., aircraft (fixed and rotary wing), weapon (rifles, pistols, rocket launchers, cannons, etc.), pelorus (also known as an astrolobe or ship's transit and used for maritime navigation) telescopes (used for spotting purposes for large astronomical telescopes, both optical and radio), television cameras and the like. This listing is not intended to be exclusive, but, rather, is exemplary of the wide fields of uses of this invention.